Collagen-rich tissues like arteries, skin, lung and tendons become progressively stiffer with age. These changes occur more rapidly in short vs. long-lived animals, and occur more rapidly in diabetes, suggesting that hyperglycemia accelerates the aging process. We hypothesize that many of these changes are mediated by the advanced Maillard reaction which involves reducing sugars and proteins. Progress achieved in the past five years includes 1) The isolation of two fluorescent molecules "P & M" from aging human collagen and the complete structure elucidation of one of them, i.e. pentosidine 2) the immunohistochemical localization of the advanced Maillard product pyrraline in diabetic tissues 3) the demonstration of a correlation between severity of diabetic complications and t he advanced Maillard reaction as reflected by pentosidine level 4) the discovery of uremia as a syndrome of accelerated Maillard reaction and its correctibility by renal transplantation and 5) the discovery that pentosidine levels in lens are tightly linked to the pigmentation process which is most likely due to vitamin C mediated Maillard reaction. In spite of the progress achieved in our laboratory and by other investigators, the structure of the major Maillard and collagen crosslinks in diabetes and aging remains unsolved. Therefore, in the coming 5 years, we propose; 1) to elucidate the structure of collagen- linked fluorophore M, 2) to investigate the structure of the major crosslinks resulting from the Maillard reaction involving basic amino acids and glycated residues using a novel approach based on short chain peptides 3) to define the ole of uncharged polar amino acid residues in postsynthetic modification of glycated proteins and 4) to characterize the structure of the major MR reaction intermediates present in diabetic and uremic plasma. By the end of this funding period we hope to have elucidated the major chemical pathways of the Maillard reaction under physiological conditions as a basis for in-depth studies of its biological significance.